If you "use warnings;" in the package, you get these helpful messages: 
Use of uninitialized value $class in concatenation (.) or string at An
+imal.pl line 7.
 Cow goes moooo!
Use of uninitialized value $class in concatenation (.) or string at An
+imal.pl line 13.
 Horse goes neigh!
Use of uninitialized value $class in concatenation (.) or string at An
+imal.pl line 19.
 Sheep goes baaaah!

[download]
for the stuff you say is "Non working code".

This gives a clear hint on what $class is set to when invoked that way, and why it "does not work".

             All great truths begin as blasphemies.
                   ― George Bernard Shaw, writer, Nobel laureate (1856-1950)

In reply to Re: $class name not pass in the new() by NetWallah
in thread $class name not pass in the new() by perldood

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